The diagnosis of coronary artery disease is conclusively made by visualization of coronary arteries in a cardiovascular laboratory. This test, known as coronary angiography, is a part of the more comprehensive procedure of cardiac catheterization. This latter test, besides examining the coronary arteries, also measures pressures in the different heart chambers and assesses the function of the main pumping chamber (left ventricle) of the heart. Cardiac catheterization and coronary angiography were first performed in the United States in 1959. Presently, approximately 800,000 procedures are performed in different cardiovascular laboratories in the country. Results of coronary angiography are crucial for management of coronary artery disease. Based on results of the procedure, the patient is either maintained on medical treatment, referred for bypass surgery or treated with angioplasty. Patients treated with bypass surgery or angioplasty may also require repeat coronary angiography if they again develop symptoms of coronary artery disease.
The procedure of coronary angiography involves first placing a small incision in either the groin or the arm. When performed via the groin, the procedure is called Judkin's technique and this method is much more frequent than the Sones technique which uses either arm. The present invention deals with the Judkin's technique, therefore the following description does not include coronary angiography performed through the arm. After the skin incision is made, the femoral artery is cannulated with the help of a needle. Under x-ray guidance (fluoroscopy) a guidewire is then passed through the needle into the femoral artery. After the guidewire is secured, the needle is withdrawn out of the femoral artery and out of the skin. A thin plastic tube, called the introducer sheath, is next advanced over this guidewire. Continuous access to the arterial system of the body is maintained through the introducer sheath which also provides a arterial channel through which various pre-shaped catheters are advanced. These catheters course from the femoral artery, over and beyond the aortic arch and finally are positioned under fluoroscopic guidance into the coronary arteries. Cannulation of the coronary arteries requires precise manipulation in addition to the simple advancement of the catheters. Operators choose various sequences to cannulate the coronary arteries. In the most common form, a Judkin's Left or JL catheter (FIG. 1) is first employed to cannulate the left coronary artery. Coronary cineangiography of the left coronary artery is then performed by hand injecting iodine-based radiocontrast agent ("dye") into the left coronary artery. The dye opacifies the coronary artery and simultaneous recordings over either videotape or photographic film are made to record results of the x-ray visualization of the contrast opacified coronary arteries. Visualization of coronary arteries in this manner reveals the various blockages (lesions) in the coronary arteries. Several such injections of dye are made in the various radiological projections. Different views are required for clear recognition of the various branches and to overcome confusion which can arise from overlapping of the coronary arteries. After obtaining this information about the left coronary artery, attention is focused on the right coronary artery. To obtain its diagnostic pictures, the JL catheter is exchanged for the Judkin's Right or JR catheter (FIG. 2). The procedure involves disconnecting the JL catheter from the manifold assembly located outside the introducer sheath. The guidewire is next advanced through the JL catheter which is then simultaneously withdrawn out over the guidewire and out of the introducer sheath. With the guidewire now in place, the introducer sheath is flushed with saline and a JR catheter advanced over the guidewire across the aortic arch. The guidewire is then removed and the proximal end of the JR catheter connected to the manifold for recording pressures and for injecting the dye. In comparison to the left coronary artery, the right coronary artery requires more manipulation for engaging its coronary ostium. After the catheter is placed into the origin of the right coronary artery, coronary cineangiography of the right coronary artery is performed in multiple projections in a manner similar to that used to visualize the left coronary artery. Most often a well-performed diagnostic coronary angiography utilizes between six to eight radiographic projections. It also utilizes approximately 100 to 150 milliliters of the radiocontrast agent. FIGS. 3A-3D show a JL catheter cannulating the left coronary artery and FIGS. 4A-4C demonstrate the technique used to cannulate the right coronary artery. FIG. 5 is a drawing of a normal left coronary artery, an illustration of the vessel after injection of dye in the left coronary artery. FIG. 6 similarly shows a normal right coronary artery.
The above mentioned technique is effective in the majority of diagnostic coronary angiography procedures. Although there can be a few technical variations from this standard method, most of the fundamentals are universally applicable. Rarely, a physician may employ a catheter shape other than the JR catheter to cannulate the right coronary artery. This is mostly done in case of unusual coronary anatomy. Another minor technical variation is performed by some operators who chose to completely remove the diagnostic catheter instead of exchanging it over the guidewire. The second catheter is then pre-loaded over the guidewire and advanced to cross the aortic arch when the guidewire is removed and catheterization of the artery performed in the usual fashion. Although standard radiographic projections have been prevalent for several years and are employed by the majority of operators, it is not uncommon to find the use of coronary projections which are somewhat different. Often these are selected by the physician to better highlight the coronary anatomy. On rare occasion, an operator may also decide to first perform angiography of the right coronary artery. Often, evaluation of left ventricular function is also performed in addition to coronary angiography. This is done either before or after cannulation of the coronary arteries with the help of a third type of catheter.
Common denominators besides the above variations which have remained despite decades of coronary angiography procedures include the use of two separate coronary catheters for the left and the right coronary arteries respectively, and the use of multiple radiographic projections to clearly demonstrate the entire coronary anatomy: the three main arteries and their branches.
Although the procedure of cardiac catheterization and coronary cineangiography is relatively safe, complications are present in approximately 1% of cases. Significant both in numbers as well as in their severity are complications resulting from side effects of the radiocontrast agent. All dyes cause renal injury of some degree, they can also induce abnormal heart rhythms (arrhythmias) and precipitate heart failure. There is also a clear linear relationship between the dose of the dye and complications which result from it. Dye-related problems are more commonly encountered in older patients and in patients with diabetes mellitus, kidney failure or with poor function of the left ventricle.